That would be between the renter and David. I don't think a judge would let the owner off the hook because they didn't feel David was being fair to the renter.
Outside of a couple of small variations, that is what the voucher program is. There is speculation about the company's solvency (which is really nothing more than conjecture at this point), and whether David will have the capacity to make good on those vouchers, but if we assume he does make good on it, everyone is left in the same position.
Owners get 100% of their money
Renters get their vacation At the new higher rate
Davids get their broker fee X 2
The parts of your plan that I disagree with are
I don't think this is fair to the renter. They didn't rent points, they rented a reservation. At no point did they take possession of the points and the risks associated with them.
I also don't understand why everyone is so gung-ho about the renter having to rent from the same owner. Why not mix and match so that we can fit the owner who can best offer what the renter wants? Why did you say WE?
Why? The owner got their money, the renter got their reservation, why does the broker get nothing? Where does their money go?